NAM is the official provider of online scientific reporting for the
8th International AIDS Society Conference on HIV Pathogenesis, Treatment
and Prevention (IAS 2015), which will take place in Vancouver, Canada,
19th-22nd July 2015.

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Two large studies of the 'baby-boom'
generation in the United States suggest that at least 50,000 US military
veterans have undiagnosed hepatitis C, and that around 80% of people with hepatitis C born
between 1945 and 1965 and receiving care through four large primary health care
systems could be undiagnosed. The research was presented at the 64th
meeting of the American Association for the Study of Liver Diseases (the Liver
Meeting) in Washington DC on Sunday.

Research presented at the conference also
showed that screening of pregnant women for hepatitis C on the basis of
self-disclosed risk factors would have missed almost three-quarters of
hepatitis C infections in pregnant women in the United States between 2003 and
2010.

A US recommendation to screen all adults in
the baby-boom generation (born between 1945 and 1965) was issued by the US
Centers for Disease Control and Prevention in 2012. Implementation is uneven and will depend
in part on initiatives like the recent New York state law requiring all health
facilities to screen adults in this birth cohort from January 2014, as well as
on funding.

Several studies presented at the conference
looked at the potential yield of more comprehensive age-based screening in
various settings.

Veterans

US military veterans of the baby-boom
generation form a population at higher-than-average risk of hepatitis C.
Hepatitis C prevalence is higher in adults born between 1945 and 1965 due to
higher levels of injecting drug use and greater lifetime risk of exposure to
blood transfusions containing hepatitis C compared to those born after 1965.

Veterans may be at
especially high risk of hepatitis C infection due to high levels of
injecting drug use among the population that served during the Vietnam War era
and blood exposure in battle or medical settings. Tattooing and transmission
through use of airguns for vaccination during military service are difficult to
quantify as sources of infection, but many veterans – particularly those who
did not see active service in Vietnam – believe these routes explain their
infection with hepatitis C.

Furthermore, the Veteran’s Health Administration
(VA) medical system may have an especially high prevalence of hepatitis C among
its patient population because it has tended to retain in care veterans who
have sought treatment for substance abuse through the VA system.

Lisa Backus of the Veteran Affairs Office
of Public Health presented an analysis of the proportion of veterans receiving
care through VA system who might remain undiagnosed.

The VA examined its database of 5.5 million
veterans in care to determine what proportion of patients who attended a
medical appointment in 2012 had been tested for hepatitis C between 1999 and
2012. The VA began risk-based screening for hepatitis C following a CDC
recommendation in 1998.

The researchers found that 54% of all
veterans had been screened for HCV at least once (41.5% of those born before
1945, 64.2% of those born between 1945 and 1965 and 58% of those born after 1965).

Of those screened, 95% received
confirmatory HCV RNA screening, yielding a chronic infection rate of 1.7% for
those born before 1945, 9.9% in those born between 1945 and 1965, and 1.1% for
those born after 1965.

Hepatitis C prevalence among newly-screened
veterans declined with each year – suggesting that those at greatest risk would
have been tested earlier – from 33% in 1999 to 5.7% in 2012.

Based on these rates of infection, the
researchers estimated that if the remaining 905,000 veterans in the 1945 to 1965
birth cohort underwent hepatitis C testing, an additional 51,000 veterans with
hepatitis C would be identified.

Two other studies presented at the
conference showed higher than expected prevalence of hepatitis C infection
among emergency room attendees, among pregnant women and among adults in
primary care, and demonstrated that relying on self-disclosed risk factors
alone to prompt hepatitis C testing would result in the majority of infections
going undiagnosed.

Emergency rooms

In many settings, the emergency room may be
the only site where adults – especially men – come into contact with health
services, especially if they are uninsured or have no entitlement to free
health care. Studies in the United States and Europe have shown that emergency
health care services often provide health care for people who are otherwise
disengaged from the healthcare system.

Emergency rooms also provide initial care
for a disproportionate number of older people who present with acute conditions
such as heart attack and stroke.

A study conducted over a two-week period by
the University of Alabama Birmingham in an emergency room in Alabama set out to
provide a snapshot of the prevalence of undiagnosed hepatitis C infection among
the 1945 to 1965 birth cohort.

During the study period, 874 baby boomers
were admitted, of whom 565 were willing or able to give consent for hepatitis
C testing. Twelve per cent tested positive for hepatitis C antibodies, of whom
71% were confirmed to be chronically infected with hepatitis C.

Men were more likely to test positive for
HCV (15.9 vs 8.6%, p=0.008), as were people who either lacked health
insurance or were reliant on Medicaid (16.7 vs 5.3%, p=0.001). There was no
difference in in the positivity rate between African Americans and Caucasians
(13.8 vs 10.2%, p=0.196).

Antenatal care

The American College of Obstetricians and
Gynecologists recommends HCV screening only in pregnant women “with significant
risk factors”. Analysis of 32,426,357 deliveries or miscarriages recorded in
the US Nationwide Inpatient Sample, between 2003 and 2010, identified 28,663
mothers with HCV infection. Patient records showed that in almost
three-quarters of women diagnosed with HCV at the time of delivery or
miscarriage (72%), no identifiable risk factors that might have prompted the
offer of an HCV test were recorded in the patient’s medical notes. The risk
factors analysed in this study were HIV infection, ongoing substance abuse, or
haemodialysis.

Infected women tended to be older (1.7 years older),
Caucasian, less affluent, on Medicaid, substance abusers, and have more medical
comorbidities (all P <0.001).

The study found that HCV infection was associated
with a three-fold higher risk of obstetrical pulmonary embolism, which is one of
the most common causes of death in pregnant women around the time of delivery
(adjusted odds ratio = 3.05, 95% confidence interval 1.27-7.32). The risks of early
or threatened labour (aOR 1.36, 95% CI 1.24-1.49), antepartum haemorrhage (1.44,
1.24-1.66), poor foetal growth (1.61, 1.33-1.94), and maternal thyroid dysfunction were also moderately
increased in women with HCV infection.

Primary care

The new US CDC recommendations regarding birth cohort
testing are most relevant for general practitioners, since they are the main
providers of health care for the vast majority of people in the United States.

To examine the scope for identifying previously
undiagnosed HCV infections in general medical practices, researchers carried
out an analysis of 209,076 patients from four sites who attended at least one
medical appointment between 2005 and 2010. They found that 17,464 (8.4%) had
been tested for hepatitis C, with a positivity rate of 6.4%. Three quarters of
the patients who tested positive were born between 1945 and 1965.

Logistic regression analysis identified the
following risk factors as significantly and independently associated with HCV
positivity:

Widowed or divorced marital
status (1.5, 1.2-2.0) or never married (1.4, 1.2-1.6) versus married status

Male gender (1.3, 1.2-1.6).

Applying these risk
factors to the patients in the cohort who remained undiagnosed by a multiple imputation analysis, the researchers
estimated that, if all 209,076 patients had been tested, a total of 6005 HCV-positive
cases would have been identified, a predicted prevalence of 2.9%.They estimated
that 81% of HCV infections in the cohort remained undiagnosed.

References

Backus L et al. Hepatitis C screening and prevalence among US veterans in Department of
Veterans Affairs care in 2012. 64th
Meeting of the American Association for the Study of Liver Diseases, Washington
DC, abstract 21, 2013.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.